Tumor Accumulation Ability Research Articles

Targeted Modification of the Cationic Anticancer Peptide HPRP-A1 with iRGD To Improve Specificity, Penetration, and Tumor-Tissue Accumulation.

The chimeric peptide HPRP-A1-iRGD, composed of a chemically conjugated tumor-homing/penetration domain (iRGD) and a cationic anticancer peptide domain (HPRP-A1), was used to study the effect of targeted modification to enhance the peptide's specificity, penetration, and tumor accumulation ability. The iRGD domain exhibits tumor-targeting and tumor-penetrating activities by specifically binding to the neuropilin-1 receptor. Acting as a homing/penetration domain, iRGD contributed to enhancing the tumor selectivity, permeability, and targeting of HPRP-A1 by targeted receptor dependence. As the anticancer active domain, HPRP-A1 kills cancer cells by disrupting the cell membrane and inducing apoptosis. The in vitro membrane selectivity toward cancer cells, such as A549 and MDA-MB-23, and human umbilical vein endothelial cells (HUVECs), normal cells, the penetrability assessment in the A549 3D multiple cell sphere model, and the in vivo tumor-tissue accumulation test in the A549 xenograft model indicated that HPRP-A1-iRGD exhibited significant increases in the selectivity toward membranes that highly express NRP-1, the penetration distance in 3D multiple cell spheres, and the accumulation in tumor tissues after intravenous injection, compared with HPRP-A1 alone. The mechanism of the enhanced targeting ability of HPRP-A1-iRGD was demonstrated by the pull-down assay and biolayer interferometry test, which indicated that the chimeric peptide could specifically bind to the neuropilin-1 protein with high affinity. We believe that chemical conjugation with iRGD to increase the specificity, penetration, and tumor-tissue accumulation of HPRP-A1 is an effective and promising approach for the targeted modification of peptides as anticancer therapeutics.

CRGD Peptide-Conjugated Pyropheophorbide-a Photosensitizers for Tumor Targeting in Photodynamic Therapy.

Pyropheophorbide-a (Pyro) is a highly promising photosensitizer for tumor photodynamic therapy (PDT), although its very limited tumor-accumulation ability seriously restricts its clinical applications. A higher accumulation of photosensitizers is very important for the treatment of deeply seated and larger tumors. The conjugation of Pyro with tumor-homing peptide ligands could be a very useful strategy to optimize the physical properties of Pyro. Herein, we reported our studies on the conjugation of Pyro with a cyclic cRGDfK (cRGD) peptide, an integrin binding sequence, to develop highly tumor-specific photosensitizers for PDT application. To further reduce the nonspecific uptake and, thus, reduce the background distribution of the conjugates in normal tissues, we opted to add a highly hydrophilic polyethylene glycol (PEG) chain and an extra strongly hydrophilic carboxylic acid group as the linker to avoid the direct connection of the strongly hydrophobic Pyro macrocycle and cRGD ligand. We reported here the synthesis and characterization of these conjugates, and the influence of the hydrophilic modification on the biological function of the conjugates was carefully studied. The tumor-accumulation ability and photodynamic-induced cell-killing ability of these conjugates were evaluated through both in vitro cell-based experiment and in vivo distribution and tumor therapy experiments with tumor-bearing mice. Thus, the synthesized conjugate significantly improved the tumor enrichment and tumor selectivity of Pyro, as well as abolished the xenograft tumors in the murine model through a one-time PDT treatment.

Camouflaging iRGD-EGFR anchored human cytotoxic T-lymphocyte membranes to the surface of nanoparticles combined with low-dose irradiation: New approach to enhance drug-delivery targeting in gastric cancer.

e14076 Background: We report a biomimetic delivery platform based on human cytotoxic T-lymphocyte membranes. In this platform, T-lymphocyte membranes were camouflaged to the surface of poly-lactic-co-glycolic acid nanoparticles, with local low-dose irradiation (LDI) as a chemoattractant. These carriers were further anchored with the recombinant protein anti-EGFR-iRGD, improving tumor accumulation, facilitating tumor uptake. Methods: The T-lymphocyte membrane coating was verified by dynamic light scattering, transmission electron microscopy and confocal laser scanning microscopy. The particle phagocytosis study was performed using a human phagocytic cell line. In vivo NIR fluorescence imaging was performed to monitor the route of nanoparticles. EGFR expression of tumor cells was tested before and after LDI. Results: This new platform reduced phagocytosis of macrophages by 23.99% (p = 0.002). iRGD-EGFR anchored T-lymphocyte membrane-encapsulated nanoparticles accumulated in tumor site more than unfunctionalized groups, while LDI significantly enhanced the targeting ability. LDI could up-regulate EGFR expression on tumor cells, which was important in the process of localization of iRGD-EGFR anchored T-lymphocyte membrane-encapsulated nanoparticles in tumors. Conclusions: This new platform included both the long circulation time and tumor sites accumulation ability while LDI could significantly enhance the tumor accumulation ability.

Targeted Chemo-Photodynamic Combination Platform Based on the DOX Prodrug Nanoparticles for Enhanced Cancer Therapy.

Chemo-photodynamic combination therapy has been received widespread attention in cancer treatment due to its excellent characteristics, such as reducing the adverse side effects of chemo-drugs and improving the therapeutic effects for various cancers. In this study, RGD and DOX was conjugated to PEG by thiol-ene addition and Schiff's base reaction, respectively, to prepare the targeted and pH-sensitive antitumor prodrug nanoparticles (RGD-PEG-DOX NPs, RGD-NPs). Subsequently, the photosensitizer chlorin e6 (Ce6) was encapsulated into RGD-NPs, thus obtaining a simple and efficient chemo-photodynamic combination platform (RGD-PEG-DOX/Ce6 NPs, RGD-NPs/Ce6). This nanoparticle possessed high drug loading property of both the chemo-drug and photosensitizer and could simultaneously release them under the mild acidic microenvironment of cancer cells, which was expected to realize the synchronization therapy of chemotherapy and photodynamic therapy (PDT). Compared with free DOX and Ce6, RGD-NPs/Ce6 could significantly improve the cellular uptake capacities of DOX and Ce6, resulting in the increased contents of ROS in cancer cells and effective cytotoxicity for tumor cells (MDA-MB-231 cells and MCF-7 cells) upon a laser radiation. The in vivo experiment showed that RGD-NPs/Ce6 displayed superior tumor targeting, accumulation, and retention ability than the other groups (free DOX, free Ce6 and NPs/Ce6), and thus significantly enhancing the antitumor effect in vivo with a laser radiation. In addition, the cardiotoxicity induced by DOX was thoroughly wiped out after being loaded and delivered by the nanoparticles according to the pathological analysis. Therefore, the targeted chemo-photodynamic combination therapeutic platform may be a promising candidate for enhanced cancer therapy.

GE11 peptide modified and reduction-responsive hyaluronic acid-based nanoparticles induced higher efficacy of doxorubicin for breast carcinoma therapy.

Novel breast carcinoma dual-targeted redox-responsive nanoparticles (NPs) based on cholesteryl-hyaluronic acid conjugates were designed for intracellular delivery of the antitumor drug doxorubicin (DOX). A series of reduction-responsive hyaluronic acid derivatives grafted with hydrophobic cholesteryl moiety (HA-ss-Chol) and GE11 peptide conjugated HA-ss-Chol (GE11–HA-ss-Chol) were synthesized. The obtained conjugates showed attractive self-assembly characteristics and high drug loading capacity. GE11–HA-ss-Chol NPs were highly stable under conditions mimicking normal physiological conditions, while showing a fast degradation of the vehicle’s structure and accelerating the drug release dramatically in the presence of intracellular reductive environment. Furthermore, the cellular uptake assay confirmed GE11–HA-ss-Chol NPs were taken up by MDA-MB-231 cells through CD44- and epidermal growth factor receptor-mediated endocytosis. The internalization pathways of GE11–HA-ss-Chol NPs might involve clathrin-mediated endocytosis and macropinocytosis. The intracellular distribution of DOX in GE11–HA-ss-Chol NPs showed a faster release and more efficient nuclear delivery than the insensitive control. Enhanced in vitro cytotoxicity of GE11–HA-ss-Chol DOX-NPs further confirmed the superiority of their dual-targeting and redox-responsive capacity. Moreover, in vivo imaging investigation in MDA-MB-231 tumor-bearing mice confirmed that GE11–HA-ss-Chol NPs labeled with 1,1′-dioctadecyl-3,3,3′,3′-tetramethylindotricarbocyanine iodide, a near-infrared fluorescence dye, possessed a preferable tumor accumulation ability as compared to the single-targeting counterpart (HA-ss-Chol NPs). The antitumor efficacy showed an improved therapy efficacy and lower systemic side effect. These results suggest GE11–HA-ss-Chol NPs provide a good potential platform for antitumor drugs.

Multi-Responsive "Turn-On" Nanocarriers for Efficient Site-Specific Gene Delivery In Vitro and In Vivo.

Systemic gene delivery is a complicated and multistep process that confronts numerous biological barriers. It remains a formidable challenge to exploit a single gene carrier with multiple features to combat all obstacles collectively. Herein, a multi-responsive "turn-on" polyelectrolyte complex (DNA/OEI-SSx /HA-SS-COOH, DSS) delivery system is demonstrated with a sequential self-assembly of disulfide-conjugated oligoethylenimine (OEI-SSx ) and disulfide bond-modified hyaluronic acid envelope (HA-SS-COOH) that can combat multiple biological barriers collectively when administered intravenously. DSS is designed to effectively accumulate at the tumor tissue and to be internalized into tumor cells by recognizing CD44. The multi-responsive "turn-on" DSS can respond to the alterations of hyaluronidases and glutathione at both the tumor site and at the intracellular milieu. Sequential degradation and detachment of the HA-SS-COOH envelope followed by the dissociation of the OEI-SSx/DNA inner core contributes to the activation of the endosomal escape and gene release functions, thus greatly enhancing nuclear gene delivery. A systematic investigation of DSS has revealed that the tumor accumulation ability, internalization, and endosome escape of the DSS nanocarriers, DNA unpacking and nuclear transportation are all remarkably improved by the multi-responsive "turn-on" design resulting in highly efficient gene transfection in vitro and in vivo.

Bioreducible branched poly(modified nona-arginine) cell-penetrating peptide as a novel gene delivery platform

Cell-penetrating peptides (CPPs) have been widely used to deliver nucleic acid molecules. Generally, CPPs consisting of short amino acid sequences have a linear structure, resulting in a weak complexation and low transfection efficacy. To overcome these drawbacks, a novel type of CPP is required to enhance the delivery efficacy while maintaining its safe use at the same time.Herein, we report that a bioreducible branched poly-CPP structure capable of responding to reducing conditions attained both outstanding delivery effectiveness and selective gene release in carcinoma cells. Branched structures provide unusually strong electrostatic attraction between DNA and siRNA molecules, thereby improving the transfection capability through a tightly condensed form. We designed a modified type of nona-arginine (mR9) and synthesized a branched-mR9 (B-mR9) using disulfide bonds. A novel B-mR9/pDNA polyplex exhibited redox-cleavability and high transfection efficacy compared to conventional CPPs, with higher cell viability as well. B-mR9/VEGF siRNA polyplex exhibited significant serum stability and high gene-silencing effects in vitro. Furthermore, the B-mR9 polyplex showed outstanding tumor accumulation and inhibition ability in vivo. The results suggest that the bioreducible branched poly CPP has great potential as a gene delivery platform.

In vivo synergistic antitumor effect and safety of siRNA and lonidamine dual-loaded hierarchical targeted nanoparticles

Based on development of nano-delivery system, co-delivery of chemotherapeutic drug and small interfering RNA (siRNA) has exerted a promising advantage in cancer therapy. In this work, the superiority of synergistic therapy and safety of the hierarchical targeted co-delivery system loaded with siRNA and lonidamine (LND) were evaluated. The in vivo tumor accumulation ability and cancer growth inhibition effect of the polymer-blend nanocarriers were evaluated by a H22 subcutaneous sarcoma model. Moreover, hematoxylin and eosin (H&E) staining and transferase-mediated dUTP nick end-labeling (TUNEL) staining of tumor sections from each group were compared to assess the therapeutic efficacy. The dual-loaded nanocarriers had better tumor accumulation ability, remarkably inhibited growth of solid tumor in a synergistic manner, even significantly decreased hepatotoxicity of LND, and had good in vivo biocompatibility whereas LND alone showed serious hepatotoxicity. We believed that the dual-loaded hierarchical targeted delivery system with high effectiveness and biocompatibility would provide a promising approach for cancer combination therapy.

Matrix metalloproteinases-2/9-sensitive peptide-conjugated polymer micelles for site-specific release of drugs and enhancing tumor accumulation: preparation and in vitro and in vivo evaluation.

Since elevated expression of matrix metalloproteinase (MMP)-2 and MMP-9 is commonly observed in several malignant tumors, MMPs have been widely reported as key factors in the design of drug delivery systems. Several strategies have been proposed to develop MMPs-responsive nanoparticles to deliver chemotherapeutics to malignant solid tumors. A stimuli-responsive drug delivery system, which could be cleaved by MMPs, was proposed in this study. By inserting an MMP-2/9 cleavable oligopeptide GPVGLIGK-NH2 (GK8) as spacer between α-tocopherol succinate (α-TOS) and methoxy-polyethylene glycol molecular weight (MW 2000 Da) activated by N-hydroxysuccinimide (mPEG2K-NHS), mPEG2K-GK8-α-TOS (TGK) was synthesized as the primary ingredient for MMP-2/9-sensitive micelles composed of d-α-tocopheryl polyethylene glycol 1000 succinate (TPGS) and TGK (n:n =40:60, TGK micelles). mPEG2K-α-TOS (T2K) was similarly synthesized as nonsensitive control. The TGK micelles showed better stability than nonsensitive micelles composed of TPGS and T2K (n:n =40:60, T2K micelles) owing to the inserted peptide. Fluorescence resonance energy transfer results indicated that TGK micelles could be successfully cleaved by MMP-2/9. Effective drug release was demonstrated in the presence of collagenase type IV, a mixture of MMP-2 and MMP-9. Compared with nonsensitive micelles, docetaxel (DTX)-loaded TGK micelles showed a fold higher cellular uptake in HT1080 cells. While the half-maximal inhibitory concentration (IC50) of TGK and T2K micelles were similar (P>0.05) in MCF-7 cells (MMP-2/9 underexpression), the IC50 values of the aforementioned micelles were 0.064±0.006 and 0.122±0.009 μg/mL, respectively, in HT1080 cells (MMP-2/9 overexpression). The MMP-2/9-sensitive micelles also demonstrated desired tumor targeting and accumulation ability in vivo. The results of in vivo antitumor effect evaluation indicate that TGK micelles are potent against solid tumors while maintaining minimum systemic toxicity compared with T2K micelles and DTX.

Photodynamic therapy using glycol chitosan grafted fullerenes

Glycol chitosan (GC)-grafted fullerene (GC-g-C60) conjugates were developed for use in photodynamic therapy of tumor cells. GC-g-C60 was synthesized in anhydrous benzene/dimethylsulfoxide (DMSO) co-solvent via the chemical conjugation of free amine groups of GC to CC double bonds of C60. The GC-g-C60 with 5×10−4 C60 molecules per one repeating unit of GC was soluble in water. As C60 molecules conjugated to GC increased to 0.16 molecules per one repeating unit of GC, GC-g-C60 started to form supramolecular assemblies (∼30nm) stabilized in phosphate buffer saline (PBS, 150mM, pH 7.4). Upon 670nm light illumination, photo-responsive properties of GC-g-C60 allowed tremendous singlet oxygen generation in tumor cells for super phototoxicity. GC-g-C60 also showed highly increased tumor accumulation ability for in vivo tumor of KB tumor-bearing nude mice. It is expected that our GC-g-C60 conjugate may be a good candidate for in vivo photodynamic therapy in various malignant tumor cells.